Nondestructive testing of austenitic welds using method of ultrasonic array

Under the action of welding thermal cyclic load, the internal peritectic structure of austenitic stainless steel weld is coarse columnar crystal, and its orientation is anisotropic in different areas of the weld. The nondestructive testing of austenitic stainless steel welds is conducted using method of ultrasonic array for the ultrasonic scattering caused by coarse columnar crystals and the sound beam deflection caused by different grain orientations. A signal analysis method based on decomposition of the time-reversal operator is developed for noise reduction processing of ultrasound full matrix data. Using ray tracing method, the ultrasonic wave propagation path determination method in anisotropic media was investigated and applied to the correction of beam deflection for ultrasonic array total focus imaging of austenitic stainless steel welds. Nondestructive testing of austenitic stainless steel welds was conducted using ultrasonic array, and the results showed that the time-reversal operator-based decomposition method was effective for the suppression of scattering noise in the detection signal and highlight the echoes from defects, which can improve the signal-to-noise ratio of full-focus imaging by 10 dB, moreover the beam deflection correction can improve the accuracy of defect localization in total focus imaging of ultrasonic arrays.